Under the connection to a weak grid,the Doubly Fed Induction Generator(DFIG)based wind power system has potential risk from two operational issues.The first issue is the High Frequency Resonance(HFR)mode due to the im...Under the connection to a weak grid,the Doubly Fed Induction Generator(DFIG)based wind power system has potential risk from two operational issues.The first issue is the High Frequency Resonance(HFR)mode due to the impedance interaction between the DFIG system and the weak grid.In order to ensure safe and reliable operation of the DFIG system,it is necessary to implement effective active damping strategies to mitigate the HFR.The second issue is low order voltage harmonic distortion at the Point of Common Coupling(PCC),where consequently the performance of other grid-connected devices may deteriorate.It could be advantageous that the DFIG system is able to improve the voltage quality at PCC by eliminating the low order harmonic components.In this paper,both of the above mentioned DFIG operational characters,i.e.,active damping of HFR and the improvement of voltage quality at PCC,will be achieved by implementing advanced control strategies in the Rotor Side Converter(RSC)and the Grid Side Converter(GSC)respectively.Simulations are provided to verify the proposed control strategies for DFIG system connected to a weak grid.展开更多
When a doubly-fed induction generator(DFIG)is connected to a weak grid,the coupling between the grid and the DFIG itself will increase,which will cause stability problems.It is difficult to maintain the tracking accur...When a doubly-fed induction generator(DFIG)is connected to a weak grid,the coupling between the grid and the DFIG itself will increase,which will cause stability problems.It is difficult to maintain the tracking accuracy and robustness of the phase-locked loop(PLL)in the weak grid,and the risk of instability of the current-controlled DFIG(CC-DFIG)system will increase.In this paper,a new type of voltage-controlled DFIG(VC-DFIG)mode is adopted,which is a grid-forming structure that can independently support the voltage and frequency with a certain adaptability in the weak grid.A small-signal impedance model of the VC-DFIG system is also established.The impedance of DFIG inevitably generates coupling with the grid impedance in the weak grid,especially in parallel compensation grids,and results in resonance.On the basis of the VC-DFIG,impedance stability analysis is performed to study the influences of the control structure and short-circuit ratio.Then,a feedforward damping method is proposed to modify the impedance of the VC-DFIG system at resonance frequencies.The proposed fractional order damping is utilized,which can enhance the robustness and rapidity of resonance suppression under parameter fluctuations.Finally,the experimental results are presented to validate the effectiveness of the proposed control strategy.展开更多
The impact of large-scale grid-connected wind farms of Doubly-fed Induction Generator (DFIG) type on power system transient stability is elaborately discussed in this paper. In accordance with an equivalent generator/...The impact of large-scale grid-connected wind farms of Doubly-fed Induction Generator (DFIG) type on power system transient stability is elaborately discussed in this paper. In accordance with an equivalent generator/converter model, the comprehensive numerical simulations with multiple wind farms of DFIG type involved are carried out to reveal the impact of wind farm on dynamic behavior of existing interconnected power system. Different load models involving nonlinear load model and induction motor model are considered during simulations. Finally, some preliminary conclusions are summarized and discussed.展开更多
For the recent expansion of renewable energy applications, Wind Energy System (WES) is receiving much interest all over the world. However, area load change and abnormal conditions lead to mismatches in frequency and ...For the recent expansion of renewable energy applications, Wind Energy System (WES) is receiving much interest all over the world. However, area load change and abnormal conditions lead to mismatches in frequency and scheduled power interchanges between areas. These mismatches have to be corrected by the LFC system. This paper, therefore, proposes a new robust frequency control technique involving the combination of conventional Proportional-Integral (PI) and Model Predictive Control (MPC) controllers in the presence of wind turbines (WT). The PI-MPC technique has been designed such that the effect of the uncertainty due to governor and turbine parameters variation and load disturbance is reduced. A frequency response dynamic model of a single-area power system with an aggregated generator unit is introduced, and physical constraints of the governors and turbines are considered. The proposed technique is tested on the single-area power system, for enhancement of the network frequency quality. The validity of the proposed method is evaluated by computer simulation analyses using Matlab Simulink. The results show that, with the proposed PI-MPC combination technique, the overall closed loop system performance demonstrated robustness regardless of the presence of uncertainties due to variations of the parameters of governors and turbines, and loads disturbances. A performance comparison between the proposed control scheme, the classical PI control scheme and the MPC is carried out confirming the superiority of the proposed technique in presence of doubly fed induction generator (DFIG) WT.展开更多
This paper focuses on the small-signal stability of power system integrated with DFIG-based wind farm. The model of DFIG for small-signal stability analysis has built;the 3-generator 9-bus WECC test system is modified...This paper focuses on the small-signal stability of power system integrated with DFIG-based wind farm. The model of DFIG for small-signal stability analysis has built;the 3-generator 9-bus WECC test system is modified to investigate the impacts of large scale integration of wind power on power system small-signal stability. Different oscillatory modes are obtained with their eigenvalue, frequency and damping ratio, the results from eigenvalue analysis are presented to demonstrate the small-signal stability of power system is enhanced with the increasing output of the wind farm.展开更多
This paper modeled a doubly fed induction generator (DFIG) - based offshore wind farm integrated through a voltage source converter –based high voltage direct current (VSC-HVDC) transmission system, which is collecte...This paper modeled a doubly fed induction generator (DFIG) - based offshore wind farm integrated through a voltage source converter –based high voltage direct current (VSC-HVDC) transmission system, which is collected with infinite bus for small signal stability analysis. The control system of HVDC system is considered for the stability analysis. The impact of the VSC control parameters on the network stability is studied. The lineared dynamic model is employed to do small signal stability analysis by the eigenvalue analysis. The locus of the eigenvalue, which is corresponding to the oscillation model is studied. Time domain simulations conducted in Matlab/Simulink are used to validate the small signal stability analysis.展开更多
The performance of a 1.5 MVA wind-power Doubly Fed Induction Generator （DFIG） under network fault is studied using simulator developed in MATLAB-SIMULINK. This paper investigates a new control method able to improve...The performance of a 1.5 MVA wind-power Doubly Fed Induction Generator （DFIG） under network fault is studied using simulator developed in MATLAB-SIMULINK. This paper investigates a new control method able to improve the fault-ride through capability of DFIG. In such generators the appearance of severe voltage sags at the coupling point make highlight important over currents at the rotor/stator windings, making the use of crowbar protection device necessary and inevitable in order to protect the machine as well as the rotor side power converter. The simulator consists of the DFIG analytical model, power transformer model and the detailed frequency converter model including crowbar protection device. Simulation results are carried out to show the transient behavior of the DFIG when a sudden voltage dip is introduced with and without the crowbar implementation.展开更多
This paper focuses on the small signal stability analysis of Doubly-Fed Induction Generator (DFIG) fed wind power system under three modes of operation. The system stability is affected by the influence of electromech...This paper focuses on the small signal stability analysis of Doubly-Fed Induction Generator (DFIG) fed wind power system under three modes of operation. The system stability is affected by the influence of electromechanical oscillations, which can be damped using Power System Stabilizer (PSS). A detailed modeling of DFIG fed wind system including controller has been carried out. The damping controller is designed using fuzzy logic to damp the oscillatory modes for stability. The robust performance of the system with controllers has been evaluated using eigen value analysis and time domain simulations under various disturbances and wind speeds. The effectiveness of the proposed fuzzy based PSS is compared with the performance of conventional PSS implemented in the wind system.展开更多
The utilization of wind generation equipment, such as DFIGs （double fed induction generators）, interconnected to islanded power generation and distribution systems is investigated in order to determine their effects...The utilization of wind generation equipment, such as DFIGs （double fed induction generators）, interconnected to islanded power generation and distribution systems is investigated in order to determine their effects on the overall system operating characteristics and stability. The use of a stable power station （with high speed machines） will be critical in achieving fast and reliable transient response to network events, in particular, when large transient loads are expected on a continuous basis, i.e., industrial mining and mineral processing equipment. Simulation results of this paper assist in understanding how small power stations and wind generation equipment respond to large transients in an islanded network. In particular, detailed simulations and analyses will be presented on impacts of distributed wind generation units （1.5 MW DF1G） on the stability of a small weak network. The novelty of this paper is on detailed analyses and simulation of weak networks with interconnects DFIG＇s including their impacts on system stability under various transient operating conditions.展开更多
针对双馈感应发电机(doubly-fed induction generator,DFIG)经电压源变流器–高压直流(voltagesourceconverterhigh voltage direct current,VSC-HVDC)并网,基于"主网频率-直流电压-风电场"串级下垂控制调频策略,建立DFIG经VS...针对双馈感应发电机(doubly-fed induction generator,DFIG)经电压源变流器–高压直流(voltagesourceconverterhigh voltage direct current,VSC-HVDC)并网,基于"主网频率-直流电压-风电场"串级下垂控制调频策略,建立DFIG经VSC-HVDC参与系统一次调频的动态潮流模型,用于量化DFIG备用与直流电容虚拟惯量协同控制下电网频率响应。计及DFIG有功备用,在直流电压限制范围内,提出直流电容虚拟惯性时间常数的取值上限。考虑调频过程中DFIG转速变化,提出基于转子动能的DFIG惯性时间常数动态修正算法,提高动态潮流结果精度。算例验证了所提算法分析DFIG与VSC-HVDC协同电网调频能力的可行性,证实计及DFIG参与调频的直流电容虚拟惯性时间常数最大取值可提升交流系统惯性水平;DFIG等效惯性时间常数修正算法符合其动态调频特性。展开更多
文摘Under the connection to a weak grid,the Doubly Fed Induction Generator(DFIG)based wind power system has potential risk from two operational issues.The first issue is the High Frequency Resonance(HFR)mode due to the impedance interaction between the DFIG system and the weak grid.In order to ensure safe and reliable operation of the DFIG system,it is necessary to implement effective active damping strategies to mitigate the HFR.The second issue is low order voltage harmonic distortion at the Point of Common Coupling(PCC),where consequently the performance of other grid-connected devices may deteriorate.It could be advantageous that the DFIG system is able to improve the voltage quality at PCC by eliminating the low order harmonic components.In this paper,both of the above mentioned DFIG operational characters,i.e.,active damping of HFR and the improvement of voltage quality at PCC,will be achieved by implementing advanced control strategies in the Rotor Side Converter(RSC)and the Grid Side Converter(GSC)respectively.Simulations are provided to verify the proposed control strategies for DFIG system connected to a weak grid.
基金supported by the National Natural Science Foundation of China(No.51877063).
文摘When a doubly-fed induction generator(DFIG)is connected to a weak grid,the coupling between the grid and the DFIG itself will increase,which will cause stability problems.It is difficult to maintain the tracking accuracy and robustness of the phase-locked loop(PLL)in the weak grid,and the risk of instability of the current-controlled DFIG(CC-DFIG)system will increase.In this paper,a new type of voltage-controlled DFIG(VC-DFIG)mode is adopted,which is a grid-forming structure that can independently support the voltage and frequency with a certain adaptability in the weak grid.A small-signal impedance model of the VC-DFIG system is also established.The impedance of DFIG inevitably generates coupling with the grid impedance in the weak grid,especially in parallel compensation grids,and results in resonance.On the basis of the VC-DFIG,impedance stability analysis is performed to study the influences of the control structure and short-circuit ratio.Then,a feedforward damping method is proposed to modify the impedance of the VC-DFIG system at resonance frequencies.The proposed fractional order damping is utilized,which can enhance the robustness and rapidity of resonance suppression under parameter fluctuations.Finally,the experimental results are presented to validate the effectiveness of the proposed control strategy.
文摘The impact of large-scale grid-connected wind farms of Doubly-fed Induction Generator (DFIG) type on power system transient stability is elaborately discussed in this paper. In accordance with an equivalent generator/converter model, the comprehensive numerical simulations with multiple wind farms of DFIG type involved are carried out to reveal the impact of wind farm on dynamic behavior of existing interconnected power system. Different load models involving nonlinear load model and induction motor model are considered during simulations. Finally, some preliminary conclusions are summarized and discussed.
文摘For the recent expansion of renewable energy applications, Wind Energy System (WES) is receiving much interest all over the world. However, area load change and abnormal conditions lead to mismatches in frequency and scheduled power interchanges between areas. These mismatches have to be corrected by the LFC system. This paper, therefore, proposes a new robust frequency control technique involving the combination of conventional Proportional-Integral (PI) and Model Predictive Control (MPC) controllers in the presence of wind turbines (WT). The PI-MPC technique has been designed such that the effect of the uncertainty due to governor and turbine parameters variation and load disturbance is reduced. A frequency response dynamic model of a single-area power system with an aggregated generator unit is introduced, and physical constraints of the governors and turbines are considered. The proposed technique is tested on the single-area power system, for enhancement of the network frequency quality. The validity of the proposed method is evaluated by computer simulation analyses using Matlab Simulink. The results show that, with the proposed PI-MPC combination technique, the overall closed loop system performance demonstrated robustness regardless of the presence of uncertainties due to variations of the parameters of governors and turbines, and loads disturbances. A performance comparison between the proposed control scheme, the classical PI control scheme and the MPC is carried out confirming the superiority of the proposed technique in presence of doubly fed induction generator (DFIG) WT.
文摘This paper focuses on the small-signal stability of power system integrated with DFIG-based wind farm. The model of DFIG for small-signal stability analysis has built;the 3-generator 9-bus WECC test system is modified to investigate the impacts of large scale integration of wind power on power system small-signal stability. Different oscillatory modes are obtained with their eigenvalue, frequency and damping ratio, the results from eigenvalue analysis are presented to demonstrate the small-signal stability of power system is enhanced with the increasing output of the wind farm.
文摘This paper modeled a doubly fed induction generator (DFIG) - based offshore wind farm integrated through a voltage source converter –based high voltage direct current (VSC-HVDC) transmission system, which is collected with infinite bus for small signal stability analysis. The control system of HVDC system is considered for the stability analysis. The impact of the VSC control parameters on the network stability is studied. The lineared dynamic model is employed to do small signal stability analysis by the eigenvalue analysis. The locus of the eigenvalue, which is corresponding to the oscillation model is studied. Time domain simulations conducted in Matlab/Simulink are used to validate the small signal stability analysis.
文摘The performance of a 1.5 MVA wind-power Doubly Fed Induction Generator （DFIG） under network fault is studied using simulator developed in MATLAB-SIMULINK. This paper investigates a new control method able to improve the fault-ride through capability of DFIG. In such generators the appearance of severe voltage sags at the coupling point make highlight important over currents at the rotor/stator windings, making the use of crowbar protection device necessary and inevitable in order to protect the machine as well as the rotor side power converter. The simulator consists of the DFIG analytical model, power transformer model and the detailed frequency converter model including crowbar protection device. Simulation results are carried out to show the transient behavior of the DFIG when a sudden voltage dip is introduced with and without the crowbar implementation.
文摘This paper focuses on the small signal stability analysis of Doubly-Fed Induction Generator (DFIG) fed wind power system under three modes of operation. The system stability is affected by the influence of electromechanical oscillations, which can be damped using Power System Stabilizer (PSS). A detailed modeling of DFIG fed wind system including controller has been carried out. The damping controller is designed using fuzzy logic to damp the oscillatory modes for stability. The robust performance of the system with controllers has been evaluated using eigen value analysis and time domain simulations under various disturbances and wind speeds. The effectiveness of the proposed fuzzy based PSS is compared with the performance of conventional PSS implemented in the wind system.
文摘The utilization of wind generation equipment, such as DFIGs （double fed induction generators）, interconnected to islanded power generation and distribution systems is investigated in order to determine their effects on the overall system operating characteristics and stability. The use of a stable power station （with high speed machines） will be critical in achieving fast and reliable transient response to network events, in particular, when large transient loads are expected on a continuous basis, i.e., industrial mining and mineral processing equipment. Simulation results of this paper assist in understanding how small power stations and wind generation equipment respond to large transients in an islanded network. In particular, detailed simulations and analyses will be presented on impacts of distributed wind generation units （1.5 MW DF1G） on the stability of a small weak network. The novelty of this paper is on detailed analyses and simulation of weak networks with interconnects DFIG＇s including their impacts on system stability under various transient operating conditions.
文摘针对双馈感应发电机(doubly-fed induction generator,DFIG)经电压源变流器–高压直流(voltagesourceconverterhigh voltage direct current,VSC-HVDC)并网,基于"主网频率-直流电压-风电场"串级下垂控制调频策略,建立DFIG经VSC-HVDC参与系统一次调频的动态潮流模型,用于量化DFIG备用与直流电容虚拟惯量协同控制下电网频率响应。计及DFIG有功备用,在直流电压限制范围内,提出直流电容虚拟惯性时间常数的取值上限。考虑调频过程中DFIG转速变化,提出基于转子动能的DFIG惯性时间常数动态修正算法,提高动态潮流结果精度。算例验证了所提算法分析DFIG与VSC-HVDC协同电网调频能力的可行性,证实计及DFIG参与调频的直流电容虚拟惯性时间常数最大取值可提升交流系统惯性水平;DFIG等效惯性时间常数修正算法符合其动态调频特性。
